"left-hand side of a ship" (to a person on board and facing the bow), 1580s, from Middle English ladde-borde (c. 1300), perhaps literally "the loading side," if this was the side on which goods were loaded onto a ship, from laden "to load" + bord "ship's side." Altered 16c. on influence of starboard, then largely replaced by the specialized sense of port (n.1). to avoid confusion of similar-sounding words. The Old English term was bæcboard, literally "back board" (see starboard).
